Device for producing filters



MTRM- KR 292679714 Dec. 30, 1941.

2. v. BORRIES HAL; 2,257,714

DEVICE FOR PRODUCING FILTERS Filed April 29.. 1939 Patented Dec. 30,1941 DEVICE FOR PRODUCING FILTERS Bodo v.- Borries, Berlin-Spandau,Helmut Ruska,

. Berlin-Nikolassee, and Manfred vonArdenne,

Berlin-Llchterfelde, Germany,

assignors to Fides Gesellschait fiir die Verwaitung und Verwertung vongewerbllchen Schutzrechtin mit beschrankter Haftung, Berlin, Germany, acorporation of Germany Application April 29, 1939, Serial N0. 270,853 inGermany April 30, 1938 3 Claims. (Cl. 250-154 This invention relates tomeans for producing filters, in particular surface filters andultrafilters.

The high-grade filters heretofore known, including the ultra-filtersemployed in colloid chemistry, are depth filters; their filter poresextend not only straight through the filter material but also run andcurve in other directions, and their diameters vary considerably alongeach pore and between the various pores. The filter properties areusually not only determined by the dimensions of the pores but dependalso on the psychochemical condition of the walls of the hb'l'efina" dilas to form the filters. The

, fect on the charged corpuscular rays.

electrooptical lenses are preferably of the'elecdischage device forproducing filters according to the invention, and

trostatic type because of their accelerating ef-\ However, magneticlenses may also be employed, in which f u a case the total fluxtraversing a given section thereof must be relatively great owing to thesmall velocity of the heavy ccrpuscles. The irradiation unit forproducing the corpuscular rays may consist of a gas discharge tube ofthe cold cathode ray -oscillograph type or of a canal ray tube. Aboveall, canal ray tubes are suitable which, due to a particular shape ofthe electrodes, emit a highly concentrated ion current. Thus, forinstance, it has been proposed to give the anode cylinder oi a canal raytube such a shape that the beam of ion rays is focussed before passinginto the acceleration chamber and to have a magnetic field act on theions in the neighborhood of the cathode in order to dissipate thesecondary electrons released at the cathode. Such arrangements have arelatively high output of rapidly flying ions and therefore areespecially well suited for the purpose of the present invention.

The invention will be more clearly understood from the followingdescription of the embodiments diagrammatically shown in the drawing inwhich Fig. 1 shows a longitudinal section through a Fig. 2 anotherembodiment also in a longitudinal section. The source of the ion raysemployed in both embodiments consists of a canal ray tube.

In Fig. 1, I denotes the anode of the ion current source; 2 the cathode,3 the cathode aperture through which the gas chamber 4 communicates withthe vacuum chamber 5. The bottom 8 of the anode l is provided with anapercure I for the passage of the positive ions. 8 and 9 are electriclenses which render the ion beam convergent and also accelerate theions. The illustration of a voltage divider ll, having several tapsconnected with the anode cylinder 1, the cathode 2 and the lenses 8 and5, serves to indicate the relationship of the potentials applied tothese elctrodes, all of which are positive as compared with the groundpotential. The ion ray impinges on the foil H as indicated at III. Thisfoil is secured to a support l2 which may be displaced by means of anadjusting device l5 after a hole has been burnt in so that the entirefoil is gradually provided with a multitude of tiny holes. A-vacuumvessel 13 encloses all of the above-mentioned electrodes and lenses.when in operation, the gas chamber 4 may be continuously supplied withgas, and the vessel 13 may be continuously evacuated in order tomaintain the proper pressure conditions. It is preferable to I employthe same focal length for both accelerating converging lenses 8 and 9.In this case the positive ions are accelerated at both lensesapproximately at the same rate.

In the embodiment shown in Fig. 2 the twolenses i4 and i5 are insulatedfrom the grounded shields l8 and i9 surrounding the beam of ion rays,the other parts being substantially the same and designated by the samenumerals as shown in Fig. 1.

In the above-described devices. the iocussed beam of ion rays emittedfrom the irradiating unit is accelerated and fo'cussed by theelectrooptical lenses so as to have a sharply constricted cross sectionin the plane of incidence at the foil l i. Consequently, very greatenergy per unit of area is developed at the foil which is effective inburning a pore of the desired cross section through the foil. The poresproduced in this manner extend all in the same direction straightthrough the foil and have all the same diameter. The adusting deviceallows producing the pores in small and uniform distances from oneanother. The filters thus attain a high degree of uniformity and can beprepared in accurate accordance with various specifications.

What is claimed is:

1. A device for producing mechanical filters by providing a foil withfilter pores, comprising in a 5 vacuum vessel-irradiation means forproducing a beam ot'charged corpusoles heavy as compared with electronsand of an intensity sumcient tor perforating said foil when inoperation, a support for detachably holding said foil transverse to said10 beam, eiectrooptical lens means and an adjust- -able energizingcircuit connected with said lens means ior iocussing said beam toconstrict said beam in the plane of incidence in accordance with thedesired diameter or the filter pores to be '15 produced, and means formoving said foil supports laterally 01' said beam, said latter meansbeing adjustable externally of said vessel, for changing the relativeposition of said foil and said beam to produce a multitude oi. pores. 2o

2. A device for producing mechanical filters by providing a foil withfilter pores, comprising in a vacuum vessel a canal ray tube forproducing a beam of ion rays of an intensity sufilcient for perforatingsaid foil when in normal operation, a 5

support for detachably holding said I011 transverse to said beam,electrooptical means arranged between said tube and said support forfocusing said beam onto said toil, and means for moving said 1011supports laterally of said beam, said latter means being adjustableexternally of said vessel, for changing the relative position of saidfoil and said beam to produce a multitude of pores. r

3. A device for producing mechanical filters by providing a toll withfilter pores, comprising in a vacuum vessel a canal ray tube forproducing a beam of ion .rays of an intensity sufficient forperforating. said toil when in normal operation, said tube having ananode arranged and shaped so as to prefocus said beam, a support fordetachably holding said foil transverse. to said beam, electroopticalmeans arranged between said tube and said support for focussing saidbeam onto said foil, and means for moving said foil supports laterallyof said beam, said latter means being adjustable externally of saidvessel, for changing the position of said support rela- .tive to saidbeam to produce a multitude of pores.

BODO v.- BORRIES.

HELMUT RUSKA. Ma NFRED von ARDENNE.

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